1. Field of the Invention
The present invention is related to a magneto-optical recording medium processing apparatus for controlling recording and reproduction in relation to a magneto-optical recording medium, and more particularly to a magneto-optical recording medium processing apparatus for suppressing current consumption.
2. Description of the Related Art
In a magneto-optical recording medium processing apparatus, it is necessary to apply a bias magnetic field to the magneto-optical recording medium when recording to the magneto-optical recording medium, at deletion, and even at reproduction for a so-called MSR medium (a magneto-optical recording medium that utilizes magnetically-induced super resolution), which has been made practicable in recent years. A coil is used as means for generating a bias magnetic field, but when applying a bias current to a coil, slow current rise due to the affects of coil inductance must be taken into consideration.
For example, when seek is performed for moving a carriage, which guides a laser beam to a medium surface, transversely (radially) across the tracks of the medium, and positioning it at a targeted location over the surface of the medium, because current rise is slow even when a bias current begins to flow through the coil following seek, it takes a predetermined time until a bias magnetic field of the prescribed size is generated, and there are assumed to be cases in which recording, deletion, and reproduction timing (hereinafter, there are cases when these will be referred to as access timing) will be not fast enough.
FIG. 12 is a diagram illustrating a case in which a bias current is applied subsequent to seek. As shown in FIG. 12, during seek (timing t1-t2), a signal (seek current command signal) for controlling the movement of the carriage (seek) is outputted on the basis of a tracking error signal (TES), and a seek current corresponding thereto is generated. Then, subsequent to seek (timing t3), a bias current command signal for generating a bias magnetic field of a specified value is outputted, and a bias current is generated in accordance therewith. However, since bias current rise is slow in the case of FIG. 12, the bias current does not attain the specified value at access timing (timing t4), the application of a prescribed-value bias magnetic field is not fast enough, and recording, deletion and reproduction are not performed normally.
In a case like this, for example, seek is performed once again one track inwardly while the bias current is being applied as-is, and recovery processing, which repositions the carriage at a targeted location in accordance with the subsequent rotation of the medium, is executed, but wasted time and current are consumed.
To solve for this kind of malfunction, a method for applying a bias current either before starting seek or during seek is known.
FIG. 13 is a diagram illustrating a case in which a bias current is applied before seek. As shown in FIG. 13, a bias current command signal for generating a bias magnetic field of a specified value is outputted before (timing t0) the start of seek (timing t1), and in accordance therewith, a bias current is applied beforehand. Consequently, the bias current attains the specified value during seek. And then, in a state, wherein a bias current is applied as-is, a seek current command signal based on a tracking error signal (TES) is outputted, and a seek current corresponding thereto is generated. Then, in this case, since the bias current has already attained the specified value at post-seek (timing t2) access timing (timing t4), deletion, recording, and reproduction can be started immediately subsequent to seek.
However, in this case, because the seek current and bias current are applied simultaneously, the peak value of current consumption, which is the total of the seek current and bias current, increases. In line with the improved seek performance of recent years, seek current has also increased, and because of the need for even larger magnetic fields in line with increasing the density of recording media, the bias current is also showing a tendency to increase in accordance with demand for battery-powered drive and a power source for an apparatus connected via an interface. Further, in the case of a medium that requires a reproduction magnetic field, there are times when a large bias magnetic field is needed due to the characteristics of the magnetic film, and, according to circumstances, there are times that require a field larger than the recording and deletion fields. Under conditions such as these, current consumption must be reduced.